When a bone marrow biopsy is performed, a biopsy core, which consists of a plug of bone and marrow, is withdrawn with a bone marrow biopsy needle from the body of the patient. At times, it is difficult to retain the biopsy core in the needle while the needle is being withdrawn from the patient.
FIG. 1 is a schematic cross-sectional view of the known Jamshidi.RTM. bone marrow biopsy needle, which is available from Baxter Healthcare Corp. A cylindrical needle 20 tapers slightly at the distal end 22 to form a narrowed tip. An inner trocar or introducer 24 must be inserted and securely retained in the needle 20 during insertion into the patient. The trocar 24 has a chisel-like tip 26 which aids the needle to penetrate the patient's bone. After the bone is pierced, the trocar is removed rearwards from the needle and insertion of the needle continues in order to collect the desired biopsy core within the needle. Because of the inward curve of the end 22, the needle 20 has a cylindrical "dead space" 28, which is not usable to contain the biopsy core.
With the Jamshidi.RTM. needle, it is difficult to keep the solid biopsy material in the needle as the operator is withdrawing the needle from the patient. A biopsy core approximately 11/2 inches (3.8 mm) is generally needed. Conventionally, it is necessary to shake the needle from side to side, to break the biopsy core loose from the adjacent marrow. This agitation of the bone marrow is uncomfortable for the patient. It also may create a risk of metastasizing malignant cancer, leukemia, or lymphoma cells which are infiltrated in the marrow of the patient, because the bone marrow is highly vascular. The marrow contains a vascular system which is quite complex and includes a vascular sinusoidal system. See Wintrobe, M. M., et al., eds., Clinical Hematology (Lea & Febiger 1981); Anat. Rec. 68:55 (1970); and Weiss, L.,"Histopathology of the Bone Marrow," in Regulation of Hematopoiesis, A. S. Gordon, ed., (Appleton-Century Crafts 1970).
Therefore, it would be desirable to provide some means of separating or cutting the biopsy core from the surrounding marrow in order to free it for removal, without unnecessary agitation of the marrow. Such a device would be effective to reduce or eliminate risk and discomfort for the patient.
Another problem with the prior art needle is that, even after the biopsy core is broken loose from the bone marrow, it sometimes falls out of the needle as the needle is being withdrawn from the patient's body. Thus, there is a need for a biopsy needle having a closable distal end for retaining the biopsy core in the needle.